Trapping Crystal Nucleation of Cholesterol Monohydrate: Relevance to Pathological Crystallization

Abstract

Crystalline nucleation of cholesterol at the air-water interface has been studied via grazing incidence x-ray diffraction using synchrotron radiation. The various stages of cholesterol molecular assembly from monolayer to three bilayers incorporating interleaving hydrogen-bonded water layers in a monoclinic cholesterol.H(2)O phase, has been monitored and their structures characterized to near atomic resolution. Crystallographic evidence is presented that this multilayer phase is similar to that of a reported metastable cholesterol phase of undetermined structure obtained from bile before transformation to the triclinic phase of cholesterol.H(2)O, the thermodynamically stable macroscopic form. According to grazing incidence x-ray diffraction measurements and crystallographic data, a transformation from the monoclinic film structure to a multilayer of the stable monohydrate phase involves, at least initially, an intralayer cholesterol rearrangement in a single-crystal-to-single-crystal transition. The preferred nucleation of the monoclinic phase of cholesterol.H(2)O followed by transformation to the stable monohydrate phase may be associated with an energetically more stable cholesterol bilayer arrangement of the former and a more favorable hydrogen-bonding arrangement of the latter. The relevance of this nucleation process of cholesterol monohydrate to pathological crystallization of cholesterol from cell biomembranes is discussed.

Biliary cholesterol crystallization characterized by single-crystal cryogenic electron diffraction

“…Solomonov et al (24) explained that the systematic absences in the late ChIn, compared with the early ChIn, are due to the rearrangement of water molecules in the unit cell, leading to increased symmetry of a monoclinic crystal. This diffraction pattern is indexed as a monoclinic ChM phase with reflections {h, k, l ϭ h}, obeying the condition h ϩ l ϭ 2n, having an mm symmetry and belonging to the 10 ϫ 7.5 Å unit cell (24). The diffraction pattern of the second ChIn type of crystal was distinct and reproducible.…”

“…We refer to these phases as the cholesterol intermediate (ChIn) crystalline phases. Solomonov et al (24) studied cholesterol crystallizing at the air-water interface by grazingangle X-ray diffraction. In their work, they also observed a metastable form, matching the later-appearing ChIn that led to classic ChM.…”

Structure of cholesterol helical ribbons and self-assembling biological springs

“…Both studies show that thin cholesterol crystals have rectangular unit cell, with a ϭ 10 and b ϭ 7.5 Å. As the thickness increases, the rectangular unit cell transforms into the triclinic unit cell of bulk ChM (30). A striking difference between the rectangular and triclinic structures of ChM exists in the hydrogen-bonding arrangement of the water molecules interleaving the cholesterol layers.…”

“…Recent studies of cholesterol crystal nucleation upon an air-water interface (29,30), as well as diffraction electron microscopy studies of cholesterol films in bile (24), cast additional light on the pathway by which helical ribbons may be formed. Both studies show that thin cholesterol crystals have rectangular unit cell, with a ϭ 10 and b ϭ 7.5 Å.…”

Indications that Amorphous Calcium Carbonates Occur in Pathological Mineralisation—A Urinary Stone from a Guinea Pig

“…In organisms, pathological mineralization can lead to severe issues in soft tissues, the formation of mineral stones in bodily fluids, or the uncontrolled growth of hard tissues [11][12][13][14]. Organisms employ specific proteins to inhibit unwanted mineralization, which range from the blood-protein family of fetuins [11] to statherin (saliva) [15].…”